1. Field of the Invention
The present invention relates to output control systems of internal combustion engines, and more particularly, to an output control system of an internal combustion engine that controls output by halting internal combustions of cylinders.
2. Background Art
Japanese Patent Laid-open No. 2001-159326, for example, discloses a related technique for halting the combustions inside a part of the cylinders in an internal combustion engine which activates an electromagnetic valve mechanism to control output by controlling the closing timing of intake valves. This technique halts the combustions inside a part of the cylinders in the region where output is not controllable to a target value by controlling the closing timing of intake valves.
Including the above-mentioned document, the applicant is aware of the following documents as a related art of the present invention.
[Patent Document 1]
Japanese Patent Laid-open No. 2001-159326
[Patent Document 2]
Japanese Patent Laid-open No. 2000-87783
[Patent Document 3]
Japanese Patent Laid-open No. 2000-8819
[Patent Document 4]
Japanese Patent Laid-open No. Hei 8-14074
The conventional output control techniques that use cylinder halts, such as the related technique described above, are based on the concept that the number of cylinders to be halted is changed in increments of one cycle of the internal combustion engine in order to obtain a target output value. With these techniques, however, the fine control of output that uses cylinder halts is not possible. That is to say, if the output obtained when all cylinders generate positive work is taken as 100%, the output can only be controlled to either 25%, 50%, or 75%, for a four-cylinder internal combustion engine, for instance. This means that the conventional techniques make it difficult to conduct the fine control of output that uses cylinder halts, and make such control of output less feasible for a smaller number of cylinders, in particular.